/*
 * PDP-8 format converter.
 *
 * Usage: p8bin2hex tape.bin > tape.hex
 *
 * Assumes tape.bin is a SIMH-compatible paper tape image in "BIN" or "RIM"
 * formats.
 *
 * RIM format:
 *	10.000.000	leader/trailer (at least an inch of these)
 *	01.aaa.aaa	address hi (bits 5:0 contain address 11:6)
 *	00.aaa.aaa	address lo (bits 5:0 contain address 5:0)
 *	00.xxx.xxx	data hi (bits 5:0 contain data 11:6)
 *	00.xxx.xxx	data lo (bits 5:0 contain data 5:0)
 *	<repeat any number of [address, data] pairs>
 *
 * FIXME: RIM format currently almost always fails with bad checksum
 *
 * BIN format:
 *	10.000.000	leader/trailer (at least an inch of these)
 *	11.011.000	"field" (bits 6:4 specify address 14:12)
 *	01.000.010	origin hi bits: bits 5:0 contain origin 11:6
 *	00.011.100	origin lo bits: bits 5:0 contain origin 5:0
 *	00.xxx.xxx	data hi bits: bits 5:0 contain data word 11:6
 *	00.xxx.xxx	data lo bits: bits 5:0 contain data word 5:0
 *	<repeat any number of [origin, data+] sequences>
 *	00.xxx.xxx	chucksum hi - sum of all data and origin frames, but
 *	00.xxx.xxx	chucksum lo - excluding field and leader/trailer
 *
 * Some tapes may contain assembler error messages.  These are are text
 * delimited by 0377 bytes.  The BIN loader ignores bytes from starting
 * at any 0377 byte, until another 0377 byte is seen.
 */

#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>

uint16_t mem[32768];

int
load(FILE *fp)
{
	enum { Addr, Data, Leader, Fetch, Skip , Start } s = Start;
	int c = 0, n, v = 0;
	uint16_t a = 0, d = 0, t = 0, u = 0;
	for (n = 0; (c = getc(fp)) != EOF; ++n) {
		switch (s) {
		case Addr:
			u += c;
			a |= c;
			s = Fetch;
			break;
		case Data:
			u += c;
			d |= 0x8000 | c;
			s = Fetch;
			break;
		case Fetch:
		fetch:
			if (c == 0200) {
				if ((d & 0x8000) != 0) {
					if ((d & 07777) != (t & 07777))
						fprintf(stderr, "\nbad checksum %05o\n", t & 07777);
					else
						v = 1;
				}
				goto leadout;
			}
			t += u;
			u = 0;
			if (d & 0x8000) {
				mem[a] = d & 07777;
				a = (a & ~07777) | ((a + 1) & 07777);
				d = 0;
			}
			if ((c & 0300) == 0000) {
				u = c;
				d = (c & 077) << 6;
				s = Data;
				break;
			}
			if ((c & 0300) == 0100) {
				u = c;
				a = (a & ~07777) | (c & 077) << 6;
				s = Addr;
				break;
			}
			if ((c & 0307) == 0300) {
				a = ((c & 0070) << 9) | (a & 07777);
				break;
			}
			if (c == 0377) {
				s = Skip;
				break;
			}
			break;
		case Leader:
		leader:
			if (c != 0200) {
				s= Fetch;
				goto fetch;
			}
			break;
		case Skip:
			if (c == 0377) {
				s = Fetch;
				putchar('\n');
			} else {
				putchar(c);
			}
			break;
		case Start:
			if (c == 0200) {
				s = Leader;
				goto leader;
			}
			break;
		}
	}
 leadout:
	while ((c = getc(fp)) != EOF)
		;
	putchar('\n');
	return v;
}

void
dump()
{
	printf("// Generated by p8bin2hex");
	unsigned int nextaddr = -1;
	for (uint_fast32_t a = 0; a < 32768; ++a) {
		if (mem[a] == 0) continue;
		if (nextaddr != a)
			printf("\n@%x", (unsigned int)a);
		nextaddr = a + 1;
		printf(" %03x", mem[a]);
	}
	printf("\n");
}

int
main(int argc, char *argv[])
{
	if (argc != 2) {
		fprintf(stderr, "usage: p8 filename.bin\n");
		exit(EXIT_FAILURE);
	}
	FILE *fp = fopen(argv[1], "rb");
	if (!fp) {
		perror(argv[1]);
		exit(EXIT_FAILURE);
	}
	if (!load(fp))
		exit(EXIT_FAILURE);
	fclose(fp);
	dump();
	exit(EXIT_SUCCESS);
}